Mechanistic Insight into Bimetallic CoNi-MOFs Arrays with Enhanced Performance for Supercapacitors
Engineering multicomponent electroactive materials is an effective strategy to improve electrochemical performance by adjusting atomic and electronic structure. In this work, we directly synthesize oriented bimetallic CoNi-MOF nanosheets on CFP (carbon fiber paper). The CoNi-MOF/CFP shows high specific capacitance, outstanding rate capability and long cycle stability compared to monometallic Ni-MOF or Co-MOF. By adjusting Co/Ni molar ratio, CoNi23/CFP (Co:Ni = 2:3) displays the highest specific capacitance (2033 F g-1 at 1 A g-1). The introduction of Co into Ni-MOF matrix shortens Co/Ni-centered bond distances, resulting in improved bond strength, facilitating the charge transfer and increasing the electrical conductivity of CoNi-MOF, which were proved by X-ray absorption fine structures spectrum (XAFS), high angle annular dark field image (HAADF)， and electrochemical impedance spectroscopy (EIS). Our study demonstrates the origins of performance improvements and, therefore, may provide a feasible scheme to unlock the high performance MOF electrode materials.